1. Field of the Invention
The present invention relates to a data communications system, and more particularly, to a data transfer device that comprises a dedicated interface for detecting a fault, namely, an abnormal state, detects the abnormal state, and can take a necessary measure when the fault occurs in the inside of the device, a partner device, a bus, etc., for example, in a system where a plurality of appliances are connected by a digital bus, and to a method detecting such an abnormal state in a data transfer.
2. Description of the Related Art
If data is transferred or shared between information processing devices, the data is passed between the information processing devices. In this case, the data passing is implemented by adopting some interface.
For example, in a field of personal computers, interface standards such as IEEE1394, USB, Advanced Technology Attachment (ATA) which is an interface for connecting a hard disk etc., Peripheral Component Interconnect (PCI) as a standard of a bus of a personal computer etc. are adopted, and a mutual communication is implemented based on a standard between devices which conform to each standard.
Generally, in a communications system, a local device is also expected to be used under an ill environment such as a high temperature, noise, etc. even if a partner device stably operates. As a matter of course, a reverse case occurs. As performance required in a communications system, stable operations of a device are important in addition to a transfer rate, transfer efficiency, etc. Especially, for a device which transfers important data, and a device used under a harsh condition, the necessity for stable operations is high.
For safety, fault detection, etc. in such a communications system, the following conventional techniques exist.
[Patent Document 1]
Japanese Patent Publication No. HEI10-224384 “Digital Bus Fault Detecting Device”
[Patent Document 2]
Japanese Patent Publication No. 2000-358040 “Communications Network and Communications Device”
[Patent Document 3]
Japanese Patent Publication No. 2001-77881 “Packet Communications Network System”
[Patent Document 4]
Japanese Patent Publication No. 2002-300176 “Data Communications Device, Data Communications Method, Program of a Data Communications Method, and Storage Medium Recording the Program of the Data Communications Method”
Patent Document 1 discloses a fault detecting device that can easily recognize a fault of a digital bus by reading a picture signal or a control signal transmitted via a digital bus, by detecting the existence/non-existence of data from the read signal, and by lighting up an LED if the data does not exist.
Patent Document 2 discloses a communications device that comprises a switch unit disconnecting a link between nodes, and quickly forms a route bypassing a location of a fault if a node which cannot maintain a proper connection relationship exists.
Patent Document 3 discloses a network system that can automatically restore from an abnormal state without disconnecting a communication by detecting reset request data from a base station, and by making a reset, for example, if the abnormal state of a mobile terminal is detected.
Patent Document 4 discloses a technique for a stable data communication, which executes a process for a logical connection with a bus by detecting a logical disconnection from the bus even when disturbance noise caused by static electricity, etc. mixes.
However, such conventional techniques have a problem that automatically restoring a data transfer system when the system performs a misoperation is difficult in many cases. Especially, in a communication where complex protocols are required in a high-speed operation, a misoperation is sometimes caused by an external factor such as noise mixture, an instantaneous voltage drop, etc., etc., the communication is halted, and restoration becomes difficult.
Also when standardized communications protocols such as IEEE1394 and USB, there arises a problem that an unexpected state occurs depending on an operation of a communications device on the side of a connection partner, and a communication cannot be made. Although a data transfer between the partner device and a local device must be guaranteed in such a universal bus, also a problem of compatibility between connecting appliances occurs in reality.
With the IEEE1394 standard, a bus reset can be automatically made to attempt restoration in correspondence with an occurring situation. However, its execution conditions are restrictive and not sufficient. Additionally, in a situation where a bus reset often occurs, data transfer efficiency significantly deteriorates.
Furthermore, with the IEEE1394 standard, a read of a register within a protocol controller which controls communications protocols can be made with a standard interface in order to detect a fault. However, if such an operation is performed, data reception or an interrupt display as a normal operation is hindered. Besides, if a circuit which configures the standard interface function stacks, also a register read cannot be made.